I've kept a journal since I was 11. That was in the mid 80's. I hadn't heard the word “journaling” until about a year or so ago, and lately it appears that giving advice and howto information about journaling is a bit of a cottage industry. I had no idea so many people were in demand of this information, but in a world where you can subscribe to multiple very successful monthly magazines about running, I shouldn't be so shocked.
I should also not be shocked to learn that people have heard some of the benefits people tout about journaling and want those benefits for themselves. But maybe some are skeptical and wonder “is journaling really all it's cracked up to be?” For those folks, let me say this: I've read a few of the blogs myself, and while I'd say the authors are mostly 1 or 2-year “veterans” who don't really get it yet, the benefits they say you can get from journaling are not only possible, they're just the tip of the iceberg.
The key to getting started, though, is probably to completely ignore everything you've read, go get a Pilot v5 pen, and some kind of blank book, and just start doing as you please. Beyond encouraging words and listing the benefits, what the books and blogs are telling you to do is, quite honestly, bullshit. They're either trying to put arbitrary rules around it, or telling you about the process they themselves find useful… for them. Some things I read seemed utterly destructive to some of the benefits. Tread carefully around advice, from me or anyone else.
Journaling is ultimately a personal thing. All of it. Not just the process, but the goals or what you want to get out of it. Furthermore, most of the goals I've achieved over multiple decades of journaling (and they are both countless and priceless) happened not because I willed it to be so and structured my process or writing to meet them, but by happy accident. I was benefitting from journaling long before I even realized what journaling had brought to my life.
So the idea that you can learn to journal strikes me as pretty odd. But I do encourage you to do it. Just find some quiet time, a blank page, and a pen, and spill it. Even if it looks boring. In the meantime, if you have questions best answered by someone who has been doing this for more than a year or two, let me know and I'll be happy to help if I can.